Fixing flakiness of TextureLayerChangeInvisibleMailboxTest

cc/trees/single_thread_proxy.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/single_thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/memory/ptr_util.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 407 matching lines @@
 void SingleThreadProxy::SetBeginFrameSource(BeginFrameSource* source) {
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->SetBeginFrameSource(source);
 }
 
 void SingleThreadProxy::DidReceiveCompositorFrameAckOnImplThread() {
   TRACE_EVENT0("cc,benchmark",
                "SingleThreadProxy::DidReceiveCompositorFrameAckOnImplThread");
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->DidReceiveCompositorFrameAck();
-  layer_tree_host_->DidReceiveCompositorFrameAck();
+  // We do a PostTask here because freeing resources in some cases (such as in
+  // TextureLayer) is PostTasked and we want to make sure ack is received after
+  // resources are returned.
+  task_runner_provider_->MainThreadTaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&SingleThreadProxy::DidReceiveCompositorFrameAck,
+                            weak_factory_.GetWeakPtr()));
 }
 
 void SingleThreadProxy::OnDrawForCompositorFrameSink(
     bool resourceless_software_draw) {
   NOTREACHED() << "Implemented by ThreadProxy for synchronous compositor.";
 }
 
 void SingleThreadProxy::NeedsImplSideInvalidation() {
   DCHECK(scheduler_on_impl_thread_);
   scheduler_on_impl_thread_->SetNeedsImplSideInvalidation();
@@ skipping 348 matching lines @@
 
 void SingleThreadProxy::DidFinishImplFrame() {
   layer_tree_host_impl_->DidFinishImplFrame();
 #if DCHECK_IS_ON()
   DCHECK(inside_impl_frame_)
       << "DidFinishImplFrame called while not inside an impl frame!";
   inside_impl_frame_ = false;
 #endif
 }
 
+void SingleThreadProxy::DidReceiveCompositorFrameAck() {
+  if (layer_tree_host_)

[danakj, 2017/04/04 19:20:54]

This is unusual in this file, the host is only null after Stop() happens. After
which the proxy is destroyed IIRC. Can you explain why it's here?

[Saman Sami, 2017/04/04 19:32:31]

I'm not familiar with lifetime of layer_tree_host_ compared to the proxy so I
thought this check will be useful. I'll get rid of it.

[danakj, 2017/04/04 19:36:21]

I'm quite against branches just-in-case, and want them understood and explained,
because every branch is complexity when someone else reads or wants to change
the code later. Then they'd wonder when layer_tree_host_ is null, and people
will easily cargo-cult it into other places, and it just kinda spreads. Sounds
good to remove then.

[Saman Sami, 2017/04/04 21:39:14]

Done.

+    layer_tree_host_->DidReceiveCompositorFrameAck();
+}
+
 }  // namespace cc